Colloidal CdSe/CdS Dot-in-Plate Nanocrystals with 2D-Polarized Emission

We report the synthesis and properties of a novel class of nanocrystals with mixed dimensionality: a dot-in-plate core/shell nanostructure. This system was synthesized by growing a flat, disk-shaped, CdS shell on spherical CdSe cores. The anisotropic pressure induced by the shell drastically splits the first exciton fine structure in two: the “heavy hole” and “light hole” states become separated by up to 65 meV. As a result, these nanocrystals exhibit an emission strongly polarized in two dimensions, in the plane perpendicular to the wurtzite crystal <i>c</i> axis. We use polarization measurements on single nanocrystals and ensemble anisotropy studies to confirm the nature and position of the excitonic energy levels. These nanocrystals orient spontaneously when evaporated on a substrate, enabling a precise control of the orientation of their emission dipole

Biodistribution of QDs in selected organs and tissues in function of time after injection.

<p>Mice were subcutaneously injected with 20 pmol of CuInS₂/ZnS QDs in the right anterior paw. Blood samples were collected through cardiac puncture. Mice were then sacrificed at 1 h, 4 h, 8 h, 3 days, 7 days and 3 months after injection and organs were subjected to mass spectroscopy (ICP-MS). The indium concentrations in RALN, RLTLN, injection point, spleen, liver and blood were expressed as the quantity of indium (in µg) per gram of tissue or per milliliter of blood. Data are mean ± SD (n = 3 per group).</p

Cumulative indium content in excretions of mice after subcutaneous QDs administration.

<p>Mice were subcutaneously injected with 20 pmol of CuInS₂/ZnS QDs, urine (white) and faeces (gray) were collected daily and subjected to mass spectroscopy (ICP-MS). The indium contents were cumulated every day and were expressed as percentage of injected dose (% ID). Data are mean ± SD (n = 3 per group).</p

Mapping of sentinel lymph node (SLN) of tumour-bearing mice 15 min after sc. injection of 20 pmol of CuInS₂/ZnS QDs in the right anterior paw.

<p>Metastatic cells were detected in lymph node by CK19 expression using immunohistochemistry (IHC, n = 25) or molecular biology analysis (RT-qPCR, n = 28).</p><p>Data are mean ± SD.</p

Cytotoxicity of CdTeSe/ZnS or CuInS₂/ZnS QDs on normal fibroblasts.

<p>MRC-5 cells viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.</p><p>Concentration of QDs causing 50% of cell death (IC₅₀) was measured 24 h or 48 h after exposure.</p><p>Data are mean ± SD (n = 6 per condition).</p

Histology of sentinel lymph node sections of tumour-bearing mice.

<p>Sections were subjected to CK19 immunohistochemistry and hematoxylin staining. Black scale corresponds to 100 µm, the arrow indicates the metastatic invasion of the cortical sinus.</p

Assessment of QDs fluorescence intensity and indium content at different post-administration times.

<p>Kinetics of QDs fluorescence (open circle) and In content (close square) in the RALN after s.c. administration of 20 pmol of CuInS₂/ZnS QDs in mice. The indium quantity was measured by inductively coupled plasma – mass spectroscopy (ICP-MS) and expressed in percentage of injected dose (% ID). Data are mean ± SD (n = 3 per group) and indium quantity values marked with an asterisk were significantly different from corresponding fluorescence values (<i>p</i><.05).</p

Sequence of primers used for real-time qPCR of cytokeratin 19 and â actin.

<p>Sequence of primers used for real-time qPCR of cytokeratin 19 and â actin.</p